Process relating to the operation of explosion turbines



Jan. 12, 1943.

H. HoCiw RTH 2,307,789

PRocgss RELATING TO mam OPERATION OF EXELOSIOk TURBIN-ES Filed Aug. 30, 1940 3 Sheets-Sheet l I INVEINZTO'R /f f/OL WARTH Jan. 12, 1943. H. HOLZWARTH 2,307,789

PROCESS RELATING TO THE OPERATION OF EXPLOSION TURBINES Filed Aug. :50, 1940 s sheets-sheets v BYH. 73ZNARTH I ATTORNEYS Jan. 12, 1943. HQLZWARTH 2,307,789

PROCESS RELATING TO THE OPERATION OF EXPLOSION TURBINES Filed Aug. 50, 1940 3 Sheets-Sheet s VINVENTOR H. HOLZNARTH ATTORNEYS Patel fled Jan 12, 1943 construction am the' emlencyrim-51mm: l a turbine depends to a yerycoflsiderable extent on the ratio of the pgripheral velbcity of the However,

efiew ammo mm" any velocity 01 the efloajon gases because explosion temperatur muat be reduced by means uncooledgxmea mam lqu, i

on u basis o ttheillwo limp.

umeam ir aucmwmeag wit ciency of the vanes had not been. accurately determined on the basis of the favorable course of the efficiency which had been theoretically determined, but had rather adapted itself in a greater measure to the course of the total emciency which was known from steam turbine construction, there would have beenno essential reason for accepting the difllculties which are connected with an increase in temperature as a result of a lower degree of expansion of thegases from the explosion chamber. The importance of the efliciency of the vanes with reference to. the total efiiciency-of an explosion turbine appeared to be negligible compared to the other losses to such an extent for constructional reasons that the rano of the peripheral velocity to the explosion gas engine.

' 'It is here where the present invention has its start:

According to this invention, it is found that contrary to all theoretical discoveries and former practical experience, the efliciency ofthe vanes of explosion turbines is, in the field hitherto covered, far below the expected value, and that an improvement in the ratio of the peripheralvelocity to the velocity ofthe fire gases in the direction of the theoretically optimumvalue must result in amarked'increase in efliciency. Ac-

. cording to the present invention, a basis for detel-mining the efilclency'and durability of the vanesis created by choosing, as a referentialquantity, the square or the peripheral velocity u v in relation to the initial heat drop H, i. e., the

explosion chamber is opened, in relation tothe pressure ,in the wheel casing.'that is, the back pressure. This comparative figure "is The method by which this figure was obtained' .will be the subject of a special discussion in thefollowing lines.

* asomso encountered considerable difiiculties. Extensive research and tests were necessary before a type of explosion turbine with a figure above the required limit of value was capable of being operated for the sole purpose of making successful measurements.

After having reached this end, it was found that the efiiciency of'the turbine had improved to an extent confirming the fact that'a normal efllciency of the vanes had been obtained. Subs sequent comparisons between tests of older types and up to date constructions resulted in determining, with suflicient accuracy, the individual sources of losses in the rank of their importance. Now it could be actually proven that the emciency of the vanes takes a course which is essentially different from that which had been expected.

The invention will be further explained with the aid of the accompanying drawings, wherein Fig. 1 shows the'relationship between the sill-- ciency and the ratio for different types of turbines; Fig. 2 shows curves indicating the relationship between the heat drop and the pressure ratio; while Fig. 3

illustrates an explosion turbine plant embodying the present invention.

In Fig. 1, curve (1' represents a well known curve showing the efficiency of two-rim Curtis heat drop of the gases at the moment when the According to the proposals of the present invention this figure must represent a greater value than a fixed value which still remains to be explained. It should preferably remain within the impossible to prove this intuitive discovery by means of tests. In order to be able to make such tests, a fundamental change in the prevailing type of explosion turbines was indispensable. For the purpose of keeping the above-mentioned figure above a value which was recognized to represent the limit, it was necessary, on the one hand. to obtain ayery high circumferential velocity and, on the other, to keep-the heat drop H low, as a result of which the final temperature after the expansion, i. e., the temperature in the wheel casing. will be very high. With the use of uncooled turbine wheels and nozzles, it was impossible to make such tests. In order to verify the Inventor's intuitive discovery, it was at first necessary to construct, though at heavy financial cost, a type'ofturbine with effectively cooled nozales and wheel. The construction of such a type wheels, according to illustration No. 219 in the book entitled Dampf and Gasturbine by Stodola (Publisher Jul. Springer, Berlin, 1922, 5th ed). This is curve 115, the ratio 11/01 of illustration No. 219 by Stodola having been converted, by giving consideration to a loss of velocity in the nozzles of 5 per cent, for application to the figure i, H Curve b shows the course of efficiency of a tworim Curtis wheel for internal combustion turbines; giving at the same time consideration to the decrease in the explosion gas velocity during the expansion, according to observations made in 1922. The the course of curve a is much more favorable than that of curve b in the case of low values, is clearly evident. Curve 0 shows the course of the curv of efiiciency of the first Curtis wheel of explosion turbines. This curve was subsequently obtained by comparative observation of the numerous measurements on various turbines and approaches, with fair accuracy, actual conditions. Curve 0 could not be obtained from limits mentioned hereinafter However, it was I tests of individual machines, since in view of the complicated process of explosion it was impossible to determine the individual losses.

The gradual determination by experience of the individual quantities of loss was possible only at the time when these quantities underwent a fundamental change due to constructional improvements and changes in the process of explosion.

The most difilcult task in this field was the determination of the influence of the aforementioned figure on the efilciency of the vanes.

To achieve this end it was necessary, as has already been stated, to proceed to the construction of fundamentally new types of wheels and nozzles, that is to say, cooled types the construction of which required considerable funds and time. Such expenditures, however, could be justified only after having gained the intuitive belief that such complicated types constitute an essential and rapid progress making up for heavy expenditures of money and time. i As is shown by the course of curve 0, this curve actually begins to fall off considerably from curve (1 below point A. This deviation begins to assume such proportions below point B that a useful total efficiency is no longer to be reckoned with. ,Since point B may be exceeded only by making use of cooled vanes and nozzle, proof had been furnished to the effect that the construction of serviceable explosion turbines without cooling their vanes and nozzles is'impossible.

Up to the present time it had not been possible to determine accurately the causes of this striking and unexpected attitude of the vanes of explosion turbines. This may chiefly be explained by the fact that the law governing the expansion in the explosion chamber is different from what must be supposed on the basis of'theoretic observations, and that, in particular, the losses of heat at the beginning of the expansion in the explosion chamber and especially beyond the explosion chamber are many times greater than the losses of heat during the further course of the expansion. Losses caused by percussion or whirling or phenomena of deviation may also have an adverse efiect. It is of decisive importance in any case that the unexpected decrease in emciency in the case of a ,low value of thefigure (which decrease, according to intuitive. belief, was bound to occur) actuallvtakes place, and that by means of improving the'flgure the possibility of a marked increase inthe efllciency of an explosion engine could be confirmed after having surmounted all obstacles.

The drawing contains all points which were subsequently determined on the basis of tests and which account for the insertion of curve o as indicated. Each separate illustrationrepresents a series of points having reference to a certain type of explosion turbines.

A close examination of the conditions as described shows that the course of curve c is a completely unexpected one. In this connection emphasis must be laid on the dimculties in. determining the efficiency of the vanes of an explosion turbine. For the mere purpose of determining the initial heat drop which is made available in the turbine wheel, all of the factors having an,

influence on the output must be-known such as the caloric value of the gas mixture, temperature prior to the explosion, efliciency of explosion. loss of heat in the fore chamber of the nozzles, losses caused by whirls in the nozzles and vanes, losses of heat in the nozzles and vanes, losses of heat to the wheel and the housing, losses by ventilae tion, losses by throttling, and so forth. The loss of heat in the vanes is thus only a small fraction of the total losses. Attention should also be paid to the fact that even Stodola and Schille have not been able to determine. though they have left It has already been stated that in view of the compllcatednature of the process in explosion turbines it is extremely dimcult to determine with complete accuracy both numerically and according to their importance the losses arising during the entire process. Certain losses are actually larger thanhas ever'been known. Asa

result of the large number of existing fundamentally different types of engines and as a result of numerous tests under various conditions,

experts gradually succeeded in gaining a general view of the influence of the individual quantities of losses under varying conditions. Today it is possible to describe and classify with fair accuracythe losses which were found during former t tests in all types hitherto constructed.

As a result it is nowposslble to determine. with sufficient accuracy, the actual efilciency of the vanes of types of explosion turbines thus far constructed and tried. This subsequent research re-. I

sulted in determining the points forming a basis for the determination of curve 0 and made it possible to gain an idea of the course of the 'efliciency of the varies with referenceto its dependency of the chosen figure.

The classification of the losses the last link or which are those found in the vanes cannot be proven with mathematic accuracy within limits mathematically 'flxed. It is also possible that this classification may be slightly changed as a result of further'experience; It must be added that the maximum and minimum value of thefigure will only hold good as long as the figure is determined by the method described herein. An

essential change in the method of determination and, for instance, likewise a considerable change in the quantities of losses and the distribution of the losses inthe theoretical calculations would shift to a-considerable extent the limits within which the efflciency of. the vanes at an admissible temperature is still satisfactory.

In order to remove thesedifliculties it is proposed that in determining the initial heat drop on which the figure is based resort be taken to a method of approximation which was already em ployed when figure curves were drawn for the first time. A- simplification of the method of;

determining the heat drop which must be taken as a basis for the flgurecurve may-be effected by establishing the heat drop in taking the heat drop from the indicator diagram by means of determining the maximum pressure and the average counterpressure and at the same time choosing a temperature of 1,500 degrees centi'grade as the initial temperature of the expansion.

., drawing the figure curve this theory-of approximation was not retained since it became evident that as a result of cold cooling, that is, cooling by means'of a relatively cold cooling. agent, as v well as the .use of large nozzle fore chambers and small explosion'chambers in the case of older types of explosion turbines the temperature at no stone unturned and made most accurate.

measurements, that the emciency of the vanes was actuallv that far below the expected value.

There was therefore the necessity of an intuitive belief on the part of the inventor in order to realize, contrary to the opinion of all experts,j.

that the efflciency of the vanes is the. last great source of loss, and, in the face of all constructional difficulties, 'to force the improvement of the figure without being able at first to prove in some way the correctness of the intuitive belief. As far as the determination of the figure curve is concerned, the following may be said:

the beginning of the expansion was essentially This could be effected by means of thermo-. dynamic examination of the processes based. with j reference to the losses, on the theoretical data which have meanwhile become available.

It is by this method that the value of them fl'gure curve has increased considerably. The examinationof the explosion process in gas tur blues with hot cooling, that is, with a method of cooling in which the cooling agent is caused to reach its boiling point, or approximately such point, while it is maintainedunder pressure, with referenceto a 2,000 kilowatt trial turbine and another unit for 5,000 kilowatts, shows that a temperature or at least 1,500 degrees centigrade at the beginning of the expansion must be taken from the blades through a nozzle II within the separating wall H and then impinge the blades I3 of the turbine rotor H. The exhausted gases esca-D at I8. when the pressure in the explosion chamber has dropped to approximately the back pressure on the turbine wheel l0, the

into consideration. It is therefore proposed to make use or the curve given in Fig. 2 in order to determine the figure for turbines to be examined ior the purpose or finding, out whether they make use of the present invention. The curve contains data showing the heat drop of the various gaseous, liquid and solidiuels under a pressure ration of 0-14 on the basis of the Pflam entropy vdiagram. These curves apply toan initial temperature of the explosion gases of 1,500 derees centigrade exactly within the limit 01 a maximum absolute pressure oi irom 20 to 50 at- ;mospheres. In practice, however, a muchgreater pressure range is likely to be covered. Curve 0 nomle valve 6 is closed and an auxiliary outlet valve I is opened to eflect discharge of the residual explosion gases against a lower back pressure,

the valve 2 being opened at such time to admit. scave in air.

- The turbine casing is provided with a cooling Jacket, as shown at It, and the cooling agent is charged into a steam separator H, from which the separated steam is delivered to a place of use,

while the unevaporated cooling agent (preferably water) is fed from the separator by means of the line II to aseries oi! pumps 2!, 30 and 33, driven applies to blast furnace gas and similar gas with 1 the usual air conte'ntgof 15 per cent in theex plosion gases, and curve b-to gasoline, benzol, gas

oil, coking plant gas, carburetted hydrogen, and hard coal gas with an air content of 40 per cent mined as i'ollowsz'.

The maximumexplosion pressure and the aver- 1' age countermeasure or the first expansion. 1. e.,-'

the average pressure in the wheel casing is de termined on the basis of the indicator With the use oi the ratio between these two pressures the maximum-heat drop is taken from tbecurveoil'igurez.

The figure is then obtained a mean 01' a divi sion of the double square-of the medium periph- .eral velocity of the first turbine wheel by the initial heat drop time determined. 1

i In the future, explosion memes willno doubt by the motors 2 8, Ila and 34,- respectively. The pump charges the cooling agent from the pipe 31 into the Jacket 20 surrounding the inlet portion 0! the explosion chamber, the cooling agent traveling from the Jacket 20 into the jacket 2|v about the main body ofthe explosion chamber inthe explosion gases. The two curvesdeflect but slightly from one; another. It is proposed that the figure for explosionturbines be deterand into the jacket 22 about the outlet end of the.

chamber, thecoolingagent passing through the vertically arranged Jacket; in series by way of the connections 31.18.. At the discharge outlet 28 the heated'coolingj agent passes by way of the conduit 20 and collecting pipe II into the steam separator- IL- In similar. fashion, the pump 30 delivers a hot cooling agent from pipe ii and the connection 30 into the central cooling space it oi the intermediate wall II, and passes thence through pipe 32 into collecting pipe 10. The

' pump 88 charges the hot cooling agent into the pipe}! and by way of the connection It it enters the cooling space 24 ot the Jacket it, the

be developed in such a way asto make it possible for the wheels to endure hshigh gas temperatures as possible. This development may likewise bring '45 about a further increase in the maximum temperature of the explosion gases. The gas temperatures will probably also increase with the con.- 7

struction 01- larger units,.especially.larger. com- 1 bustion chambers, wherebythe losses of heat will be -decreased. With temperature increasing at the beginning of the-expansion, .there is also an an extent and the initial heatdrop H givenby the heat drop of the explosion gases atthe moment of the-first opening of the explosion chamincrease in the heat drop lmderthe, same expansion ratio, that late say, the heat drop determined at a temperature 01' .1900 degrees centigrade is smaller thatthe actual heat drop.

Fig. 8 shows an explosion turbine plant employing hot cooling and embodying the present invention. One of the explosion turbines is indicated at I and is provided with scavenging and a prccharging air valve 2, a higher pressure air valve 3, a fuel inlet member 4, and spark plugs 5. After the explosion, the gases are-discharged by opening oi" a hydraulically controlled outlet or nozzle valve 0, the 8 8 5 then passing into a'nozzle 8 by which they are directed against the blades I of the turbine wheel It. The gases discharging her in relation. to the pressure in the casing of decreased to such an the first turbine .wheel is extent that the ratio is greater than 300, a beingexpressed inmeters per second, and H in kilogram-calories per normal cubic meter 01 combustion gases (referred to 0' C. and 1.83 kgJcmF).

2. Process according to claim 1, wherein the ratio is'between 300 and 500.

HANS HOLZWARTIl. 

